The present invention relates in general to fasteners. More specifically, it refers to fasteners such as screws for use in attaching a metal roof and wall panels to structural framing members to thereby erect a metal or post-frame building.
In assembling metal and post-framed buildings, or metal and steel-framed buildings such as large sheds and barns, fasteners such as screws are used to secure metal parts like a metal roof and metal panels to a wood or steel frame that has been erected in the form of the ultimate structure. Such screws or other fasteners, either self-drilling or located in apertures previously formed and aligned in the metal and underlying wood, are inserted at predetermined intervals to hold the structure together. Yet it is not aesthetically pleasing to see row after row of screw heads projecting from the side of a building, and while attempts will often be made to obscure the screw heads by painting them over with paint the same color as the metal they secure, such attempts are often clumsy and do not succeed in obscuring the fasteners because the structure of the fasteners has not been designed to accomplish the purpose of diminishing their visibility.
Of course, the fasteners, e.g., screws are utilized to accomplish a purpose: to join a metal panel to a wood framing member, and such joinder must be weather-tight; it must secure the metal and structure so that no leakage of water or other environmental hazard enters the building through the aperture in which the fastener is located, whether that aperture is preformed or is formed by a screw with a self-drilling tip. Further, there must be no metal-to-metal contact, such as that between a metal screw and the metal roof or side wall panel of the structure that has been erected. When the two metals are of different compositions, as is usually the case, an electrical current may be generated and the result will be corrosion that will over time permit the entry of water at the galvanic site, and which also will be unsightly.
It is, therefore, a primary object of the present invention to provide such metal fasteners that will effectively secure metal roofs and panels to a wood or steel frame in such a manner as to prohibit the entry of water and other environmental liquids and solids from entering the apertures in which the shafts of the fasteners are located, and will also prevent galvanic action, and subsequent corrosion, caused by unintentional metal-to-metal contact in which the fasteners are one of the metals.
It is another object of my invention to provide metal fasteners for a metal or post-frame building in which the fasteners will be so unobtrusive that for most purposes they will be invisible to the naked eye absent close examination of the exterior of the structure.
The present invention comprises a metal fastener, including a screw or similar element and an associated gasket or washer for attaching a metal structural element to another element, which may typically be of metal or wood. The metal element of the fastener usually take the form of a screw the head of which has an outersurface and a lip depending from that surface, and which form between them a head body having an inner recess defined by the substantially flat inner surface of the body, and the inner surface of the lip. It is a particular feature of my invention that the inner surface of the lip intersects the inner surface of the body at an angle greater than 90 degrees, e.g., at an angle of between about 100 and 120 degrees, most preferably at an angle of about 112.5 degrees.
The present fastener also includes a gasket or washer that cooperates with the screw to effect a tight, weatherproof connection of two articles. The gasket is located to abut the inner recess of the screw head When the screw is not under pressure to join any articles, the deformable gasket is contiguous with the inner screw body surface, but space from the inner surface of the lip of the head body. However, when the screw is under stress to hold articles together, the washer is deformed to a position in which it is contiguous with both the body and lip inner surfaces, thereby filling the recess defined by those surfaces and preventing the ingress of unwanted rain water or other foreign materials. It is preferred that under compression the gasket not extend beyond the cylindrical plane defined by the annular lip of the screw head.
As additional features of my invention, the screw head is preferably of low-profile design, providing a smooth, convex, upwardly extending but trancated surface when in place. Also, the screw driving means may be indented from the outer surface of the head so that the driving means is located entirely within the outline of the uppoer surface of the head. In addition, in order to maintain the washer in place, it is preferred that the threads located along the periphery of the screw extend substantially to the plane of the inner surface of the head body.